1. Field of the Invention
The present invention is related an image signal processing method, and more particularly to a method of converting RGB gray levels to RGBW gray levels.
2. Description of the Prior Art
With the advancement of display panel technologies, liquid crystal display (LCD) panels are widely used in portable devices such as laptops, tablet computers, and smart phones. In general, power consumption of the portable devices should be low so that the portable devices may operate over a long period of time without being charged. However, due to RGB (red, green, blue) LCD panels having low light penetration rate such that only 5˜10% of light intensity from backlight penetrates panels, energy used for illuminating panels is not fully utilized. Thus pixels should be re-designed to increase light penetration rate so as to utilize energy more efficiently and reduce power consumption of panels.
In contrast, RGBW (red, green, blue, white) LCD panels have higher light penetration rate and lower power consumption because white sub-pixels having higher light penetration rate are introduced into pixels. However, due to each sub-pixel (respectively being red, green, blue, white) of RGBW LCD panels occupying a smaller area than that of each sub-pixel of RGB LCD panels, images displayed on RGBW LCD panels are darker when the images are single colored (saturated color), and brightness may be too bright when RGBW LCD panels display all white images. Thus image quality of RGBW LCD panels may be poorer than RGB LCD panels.